Title: Visual Space Is Represented by Nonmatching Topographies of Distinct Mouse Retinal Ganglion Cell Types
Abstract: The distributions of neurons in sensory circuits display ordered spatial patterns arranged to enhance or encode specific regions or features of the external environment. Indeed, visual space is not sampled uniformly across the vertebrate retina. Retinal ganglion cell (RGC) density increases and dendritic arbor size decreases toward retinal locations with higher sampling frequency, such as the fovea in primates and area centralis in carnivores [1Wässle H. Boycott B.B. Functional architecture of the mammalian retina.Physiol. Rev. 1991; 71: 447-480PubMed Google Scholar]. In these locations, higher acuity at the level of individual cells is obtained because the receptive field center of a RGC corresponds approximately to the spatial extent of its dendritic arbor [2Peichl L. Wässle H. The structural correlate of the receptive field centre of alpha ganglion cells in the cat retina.J. Physiol. 1983; 341: 309-324Crossref PubMed Scopus (124) Google Scholar, 3Yang G. Masland R.H. Receptive fields and dendritic structure of directionally selective retinal ganglion cells.J. Neurosci. 1994; 14: 5267-5280PubMed Google Scholar]. For most species, structurally and functionally distinct RGC types appear to have similar topographies, collectively scaling their cell densities and arbor sizes toward the same retinal location [4Collin S.P. A web-based archive for topographic maps of retinal cell distribution in vertebrates.Clin. Exp. Optom. 2008; 91: 85-95Crossref PubMed Scopus (67) Google Scholar]. Thus, visual space is represented across the retina in parallel by multiple distinct circuits [5Field G.D. Chichilnisky E.J. Information processing in the primate retina: circuitry and coding.Annu. Rev. Neurosci. 2007; 30: 1-30Crossref PubMed Scopus (236) Google Scholar]. In contrast, we find a population of mouse RGCs, known as alpha or alpha-like [6Peichl L. Alpha ganglion cells in mammalian retinae: common properties, species differences, and some comments on other ganglion cells.Vis. Neurosci. 1991; 7: 155-169Crossref PubMed Scopus (121) Google Scholar], that displays a nasal-to-temporal gradient in cell density, size, and receptive fields, which facilitates enhanced visual sampling in frontal visual fields. The distribution of alpha-like RGCs contrasts with other known mouse RGC types and suggests that, unlike most mammals, RGC topographies in mice are arranged to sample space differentially.